This invention relates to a locking mechanism or arrangement for locking passenger motor vehicle rear doors with locking devices preventing unauthorized unlocking of the doors from the interior of the vehicle. Such so-called child safety lock systems, which the present invention is directed at improving, are described in German Published Patent Application No. (DE-OS 3 127 732).
In order to make the awkward manual locking and unlocking unnecessary in the case of locking mechanisms--also known as so-called child safety locks--which each have a mechanically operable bolt on the front side of each rear door which is accessible only when the door is opened and, after it is in operation, prevents the unauthorized opening of the door from the interior side of the door, it has been comtemplated to carry out the operation from the front seats of the car and without opening the rear doors. In this case, a control unit driven by an electric motor is assigned to the locking mechanism of each door lock, said control being reversible in its rotational direction via a double pole changing switch and being connected with it and said control unit being remotely operable with respect to the locking or unlocking of the lock from a switching element that can be operated from the front seats. The locking condition of the locking mechanism may in this case be indicated by an optical display, in particularly by a luminous diode.
A use of such a construction which takes safety as well as comfort into account is connected with high costs because the expenditures that are required for checking whether the child safety lock is actually switched on are considerable because an electric switch has to be mounted at the corresponding door lock which, via a twin-core cable, switches the control light arranged in the area of the switching element as an "acknowledgement".
It is therefore an objective of the invention to develop a locking mechanism of the above type with a minimum use of electromechanical switching and circuit elements and expenditures in a more cost-effective manner than heretofore provided.
According to the invention, the above-noted objective is achieved by advantageously arranging the display mechanism in a portion of the circuit for controlling the locks so that it is not necessary to provide an additional switch in each door lock including the holding means and an additional circuit line.
In especially preferred embodiments, the display means is connected in series with a p-n-p transistor having its base and collector connected respectively to "off" lines of the locking device circuits.